1. Field of the Invention
The present invention relates to jig systems and more particularly pertains to a new automatic truss jig setting system for setting and resetting jig stops in a highly efficient and effective manner.
2. Description of the Prior Art
Jig systems have been used to hold building elements, such as wood boards, in proper position while the building elements are attached to each other to construct a roof support truss. Known jig systems typically employ a horizontal surface (such as a table) for resting the building elements thereon and a plurality of adjustable stops for indicating the proper positions of the building elements in the desired truss design and for holding the building elements in those positions until the elements can be secured together in a permanent manner. For each different truss design, the stops must be repositioned on the jig surface to reflect the different positions of the building elements. Computer programs have been developed to calculate, for various truss designs, the positions of the stops from a reference line, such as an edge of the table. Conventional practice has been to measure the positions of the stops from the reference line, manually move the stops to the positions, manually secure the stops in the desired positions, place the building elements on the table against the stops, fasten the building elements together, remove the completed truss, and then repeat the process by releasing and then re-securing the stops for each different truss design.
As there can be significant variation between the size and shape of roof support trusses used for the same building, a significant amount of the truss production time has been dedicated to resetting the positions of the stops, especially when only one or two trusses for each truss design are needed. For example, the setup for positioning the stops on the truss jig may take approximately 15 minutes or more, while the time needed to actually construct the truss may be only 3 minutes.
Various approaches have been used to speed up the jig stop set up process, and one approach has been to project an image of the desired truss in actual shape and size on the surface of the jig, which can help minimize the amount of measurement required but does not eliminate the need to repeatedly secure and loosen the stops for each truss design. Further, the projection equipment and associated controlling system tends to be relatively expensive.
Another approach has been to employ a system that automatically moves the stops (sometimes referred to as xe2x80x9cpucksxe2x80x9d) along slots in the horizontal surface of the jig. While in concept these systems can save time otherwise needed to measure, move and secure the stops on the jig, there have been problems that have cropped up with these systems that make them less time saving and reliable as they could be for optimum efficiency.
For example, the environment in which the jig systems are used is filled with debris and dust. Even when the building elements are cut and shaped at a location remote from the jig system, the building elements often carry sawdust and wood chips onto the surface of the table of the jig system. This debris falls or is pushed into the slot in which the puck moves. As each puck is typically mounted on a screw-threaded rod that is positioned below the puck in the slot, the debris often falls onto the rod. Since the rod rotates to move the puck, a rod caked with debris can hamper and even prevent movement of the puck along the rod. Thus, regular and frequent cleaning of the rod is needed to minimize the possibility of breakdowns of the system.
Further complicating this situation is the fact that the screw-threaded rods typically are covered with some type of lubricant to facilitate movement of the puck along the rod, and this often sticky lubricant holds the debris on the surface of the rod. The encrusted rod can carry the debris into the cooperating parts of the system, and cause additional friction and failure.
Still further exacerbating this problem in the known systems is the placement of the rod in a channel located below the slot with a closed bottom that holds the debris in close proximity to the rod, so that infrequent clearing of the channels can bring debris in contact with the rods from the bottom (as well as from the top as debris falls from the table surface).
Still further, the known systems lack a suitable system for dealing with encounters between the puck and an obstruction while the puck is moving to the desired position. Some known systems permit slippage between the driving motor and the rod when resistance in moving the puck is encountered, but the slippage results in the system losing track of the position of the puck on the jig and the system must then be reset in some manner so that the system can reassess the position of the puck on the table and reposition each of the affected pucks to the correct positions. This is particularly a problem in systems that rely upon the precise rotation of the motor (such as a stepper motor) in order to determine the current position of the puck on the jig system. Any slippage between the motor and the rod results in the puck being in a position different from where the system registers the location of the puck.
Thus, while the known systems for automatically positioning the stops on the jig are an improvement over jig systems requiring manual positioning of the stops, there are significant new problems that have arisen with the use of these automatic systems that hamper their operation in a highly efficient and effective manner.
In view of the foregoing disadvantages inherent in the known types of jig systems known in the prior art, the present invention provides a new automatic truss jig setting system that is highly suitable for setting and resetting jig stops in a highly efficient and effective manner.
To attain this, in one aspect of the invention, the jig setting system comprises a table including a plurality of segments with side edges of adjacent segments defining a slot. A plurality of pin assemblies is movable independently of each other along the slot. Movement apparatus is provided for independently moving the pin assemblies along the slot. Each of the side edges of the segments associated with the slot defines a substantially vertical plane with a zone being defined between the substantially vertical planes of the side edges, and the movement apparatus is located substantially outside of the zone of the slot.
In another aspect of the invention, the jig setting system comprises a table including a plurality of segments with side edges of adjacent segments of the plurality of segments defining a slot. A pin assembly is movable along the slot. Movement means is provided for moving the pin assembly along the slot. The movement means includes rotation means for producing rotational motion, converting means for converting rotational motion into translational motion by the pin assembly, rotation transferring means for transferring rotational motion of the rotation means to the converting means while permitting slippage between the rotation means and the converting means when translational movement of the pin assembly is resisted, and position sensing means for sensing rotation of the converting means to determine a position of the pin assembly along the slot. Sensing of rotation of the converting means by the position sensing means is not affected by any slippage of the rotation transferring means.
An optional aspect of the invention includes detecting means for detecting interference with movement of one of the pin assemblies. The detecting means may comprise means for determining when rotational motion by the rotation means is not transferred to the converting means by the rotation transferring means, means for temporarily delaying for a predetermined time period further actuation of the rotation means when rotational motion by the rotation means is not transferred to the converting means by the rotation transferring means, and means for reinitiating rotational movement of the rotation means when the predetermined time period has passed. The detecting means may also comprise means for canceling further movement of the pin assemblies if, after a preset period of time, attempts to reinitiate rotational movement of the rotation means does not result in rotational motion by the rotation means being transferred to the converting means by the rotation transferring means.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
One significant advantage of the present invention is the ability to minimize, if not altogether prevent, the buildup of debris on (or in the proximity of) the apparatus for moving the pin assemblies so that frequently cleaning and sudden breakdowns of the apparatus can be avoided. Another significant advantage is the ability of the system to handle situations where one of the pin assemblies is prevented from moving by an obstruction.
Further advantages of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention.